Positive active material for rechargeable lithium battery, method of preparing same, and rechargeable lithium battery including same

Abstract

A positive active material for a rechargeable lithium battery including a lithium metal oxide represented by the following Chemical Formula 1, a method of preparing the same, and a rechargeable lithium battery including the same. Li a MeM′ k O 2   Chemical Formula 1 In Chemical Formula 1, Me is Ni x Co y Mn z , M′ is Mg, Al, Fe, P, or a combination thereof, 0.955≦a<1.05, 0.001≦k≦0.1, 0.5<x≦0.65, 0.1<y≦0.25, 0.1<z≦0.25, x+y+z+k=1, M′ is doped at a Li site and at least one of Ni, Co, and Mn sites, M′ is doped in an amount at 0.1 mol % or 10 mol % or between 0.1 mol % and 10 mol % based on the total amount of Ni, Co, and Mn, and a doping mole ratio of M′ doped at the Li site with respect to a Me site is in the following range: about 0.001≦A Li /A Me ≦about 0.5.

What is claimed is: 
     
       1. A positive active material for a rechargeable lithium battery comprising a lithium metal oxide represented by the following Chemical Formula 1:
   Li a MeM′ k O 2   Chemical Formula 1
 
 wherein, in Chemical Formula 1, 
 Me is Ni x Co y Mn z , M′ is Mg, 0.95≦a<1.05, 0.001≦k≦0.1, 0.5<x≦0.65, 0.1<y≦0.25, 0.1<z≦0.25, x+y+z+k=1, 
 M′ is doped at a Li site and at least one of Ni, Co, and Mn sites, 
 M′ is doped in an amount at 0.1 mol % or 10 mol % or between 0.1 mol % and 10 mol % based on the total amount of Ni, Co, and Mn, 
 a doping mole ratio of M′ doped at the Li site with respect to a Me site is in the following range: about 0.05≦A Li /A Me ≦about 0.33, and 
 wherein the positive active material has a heat flow maximum value at 10 W/g or 18 W/g or between 10 W/g and 18 W/g in a Differential Scanning Calorimetry (DSC) measurement. 
 
     
     
       2. The positive active material of  claim 1 , wherein in Chemical Formula 1, M′ is doped in the amount at 1 mol % or 4 mol % or between 1 mol % and 4 mol % based on the total amount of Ni, Co, and Mn. 
     
     
       3. A method of preparing a positive active material, for a rechargeable lithium battery the method comprising:
 preparing a precipitate by co-precipitating each metal source material comprising Ni, Co, and Mn, and a doping element (M′) source material comprising Mg, and ammonium hydroxide (NH 4 OH) or sodium hydroxide (NaOH); 
 mixing the precipitate with a lithium source material in a weight ratio at 1:1 or 1:1.05 or between 1:1 and 1:1.05; and 
 heat-treating the mixture to prepare a lithium metal oxide represented by the following Chemical Formula 1:
   Li a MeM′ k O 2   Chemical Formula 1
 
 
 wherein, in Chemical Formula 1, 
 Me is Ni x Co y Mn z , M′ is Mg, 0.95≦a<1.05, 0.001≦k≦0.1, 0.5<x≦0.65, 0.1<y≦0.25, 0.1<z≦0.25, x+y+z+k=1, 
 M′ is doped at a Li site and at least one of Ni, Co, and Mn sites, 
 M′ is doped in an amount at 0.1 mol % or 10 mol % or between 0.1 mol % and 10 mol % based on the total amount of Ni, Co, and Mn, and 
 a doping mole ratio of M′ doped at the Li site with respect to a Me site is in the following range: about 0.05≦A Li /A Me ≦about 0.33. 
 
     
     
       4. The method of  claim 3 , wherein the heat-treating is performed at a temperature at 700° C. or between 700° C. and 900° C. 
     
     
       5. The method of  claim 3 , wherein the heat-treating is performed at a temperature at 800° C. or between 800° C. and 900° C. 
     
     
       6. The method of  claim 3 , wherein the heat-treating is performed for about 8 to about 15 hours. 
     
     
       7. The method of  claim 3 , wherein the heat-treating is performed for about 8 to about 11 hours. 
     
     
       8. The method of  claim 3 , wherein the co-precipitating is performed at a reaction speed at 600 rpm or 800 rpm or between 600 rpm and 800 rpm. 
     
     
       9. The method of  claim 3 , wherein the co-precipitating is performed at pH of about 10 to about 12. 
     
     
       10. The method of  claim 3 , wherein the co-precipitating is performed for about 8 to about 10 hours. 
     
     
       11. The method of  claim 3 , wherein the co-precipitating is performed at a temperature at 35° C. or 40° C. or between 35° C. and 40° C. 
     
     
       12. The method of  claim 3 , wherein in Chemical Formula 1, M′ is doped in the amount at 1 mol % or 4 mol % or between 1 mol % and 4 mol % based on the total amount of Ni, Co, and Mn. 
     
     
       13. A rechargeable lithium battery comprising:
 a positive electrode comprising a lithium metal oxide positive active material represented by the following Chemical Formula 1; 
 a negative electrode; and 
 an electrolyte solution impregnating the positive electrode and the negative electrode:
   Li a MeM′ k O 2   Chemical Formula 1
 
 
 wherein, in Chemical Formula 1, 
 Me is Ni x Co y Mn z , M′ is Mg, 0.95≦a<1.05, 0.001≦k≦0.1, 0.5<x≦0.65, 0.1<y≦0.25, 0.1<z≦0.25, x+y+z+k=1, 
 M′ is doped at a Li site and at least one of Ni, Co, and Mn sites, 
 M′ is doped in an amount at 0.1 mol % or 10 mol % or between 0.1 mol % and 10 mol % based on the total amount of Ni, Co, and Mn, 
 a doping mole ratio of M′ doped at the Li site with respect to a Me site is in the following range: about 0.05≦A Li /A Me ≦about 0.33, and 
 wherein the positive active material has a heat flow maximum value at 10 W/g or 18 W/g or between 10 W/g and 18 W/g in a Differential Scanning Calorimetry (DSC) measurement. 
 
     
     
       14. The rechargeable lithium battery of  claim 13 , wherein in Chemical Formula 1, M′ is doped in the amount at 1 mol % or 4 mol % or between 1 mol % and 4 mol % based on the total amount of Ni, Co, and Mn. 
     
     
       15. The rechargeable lithium battery of  claim 13 , wherein the rechargeable battery has discharge capacity at 160 mAh/g or 190 mAh/g or between 160 mAh/g and 190 mAh/g.